AWD for absolute certain. AWD will ALWAYS be faster if there is a decent amount of power there. If you have an underpowered engine which doesn't peel out with just rear wheel drive, then the RWD might be faster because you have less to power and you don't have any wheel slip, but if you start getting into any significant amount of power, the AWD will always be faster because you have 4 wheels to grip your launch, which in turn means you can launch at higher rpm's without losing traction in a peel-out. This is why cars like the new Subaru WRX and other cars like the 911 Turbo AWD are so fast in 0-60 and 1/4 mile times. I know, I used to have a Syclone pickup (modified S10) which had a turbo and AWD built in, it was only makes a bit over 300hp but I could smoke RWD cars with 400hp. Although, thinking this over, there are a few exceptions, like if you had some nice slicks that you can pound the power onto, you don't need to worry about AWD, but it all depends on what situation you're looking at.